Microporous materials (pore size <20 Å) are of great technological importance for adsorption, separation and heterogeneous catalysis due to their large and accessible surface areas (typically 300-1500 m2/g). Two main classes of inorganic microporous materials, zeolites (aluminosilicate) and activated carbons, are widely used in industry. In addition, extensive research has been carried out in last ten years to produce intrinsically microporous polymeric materials (Davankov 1990, Tsyurupa 2002, Webster 1992, Urban 1995, Wood 2007, Masuda 1983, Nagai 2001, Tanaka 1992, Weber 2007, Yu 2002, Pinnau 1996, Dai 2004). These novel polymers mimic the microporous structure of inorganic materials but also offer numerous advantages, such as good processibility, broader range of physical properties and potential for introducing functionality.
During the last four years, the groups of Budd and McKeown (Budd 2004a, Budd 2004b, McKeown 2005a, Budd 2005, McKeown 2005b) have reported dioxane-based ladder polymers of intrinsic microporosity (PIMs) which possess an amorphous microporous glassy structure with good processability. These PIMs derive their properties from their highly rigid and contorted ladder structures, which can prevent efficient chain packing and offer extraordinarily high surface areas. Since the initial reports of Budd and McKeown, other groups have broadened this work to explore different polymerization techniques or produce structurally different PIMs, which maintain high permeability (e.g., oxygen permeability, PO2>100 Barrer) combined with a selectivity that often exceeds the Robeson upper bound. However, only a few such polymers have been reported that provide robust, high molecular weight materials for gas permeability measurements (Budd 2004a, Ghanem 2008, Carta 2008, Du 2008) because of the lack of suitably reactive monomers for polycondensation.
Although a fully hydrolyzed PIM-1 has been mentioned in a patent application (Scheme K, compound 71 of McKeown 2005a), no details regarding hydrolysis procedures, characterization of the main chain structure, film formation and gas separation properties were reported. Further, there is no recognition that the degree of hydrolysis can be controlled to tune the properties of the polymer.
In our previous work, monomers were synthesized for the preparation of structurally new PIMs, whereby gas permeability, selectivity and other properties were tuned to adjust the interchain spacing and to enhance the chain rigidity (Du 2008, Du in press). Although several high molecular weight PIMs were recently prepared by polycondensation of new synthetic monomers, there remains a need for polymers that may be used to provide films for a variety of gas separation applications.